Xia, Yonghui Existence of positive periodic solutions of mutualism systems with several delays. (English) Zbl 1134.34323 Adv. Dyn. Syst. Appl. 1, No. 2, 209-217 (2006). By using the coincidence degree, the author studies the global existence of positive periodic solutions for a class of mutualism systems with several delays and obtains a new and interesting criterion. Reviewer: Zhichun Yang (Chongqing) Cited in 3 Documents MSC: 34K13 Periodic solutions to functional-differential equations 92D25 Population dynamics (general) 92B05 General biology and biomathematics Keywords:coincidence degree; mutualism model PDFBibTeX XMLCite \textit{Y. Xia}, Adv. Dyn. Syst. Appl. 1, No. 2, 209--217 (2006; Zbl 1134.34323)